Cropping is the process of the removal of outer parts of an image. Cropping may take place to improve the composition of an image, or to change the aspect ratio of the image. Manually cropping digital images can be a time consuming process, therefore computer implemented automatic cropping techniques have been developed for digital images.
U.S. Pat. No. 6,654,506 discloses a method and computer system for cropping a digital image. The method includes inputting a belief map of a photographic image where the belief map includes belief values for locations in the image indicating the importance of a photographic subject at that location in the image. The method further comprises selecting a zoom factor and a crop window, clustering regions of the belief map to identify background portions, secondary portions, and main portions. The method further comprises positioning the crop window such that the crop window is centered around a main portion having a highest belief value, and moving the crop window such that the crop window is included completely within the image, and moving the crop window such that a sum of belief values is at a maximum. The image is cropped according to the crop window.
US 2002/0191861 discloses an apparatus and method relating to the automatic and semi-automatic cropping of electrical images. An electronic image processing device for cropping an electronic image comprises an image processing means which includes an electronic processor, and firmware, and/or software for processing the electronic image. The device processes the electronic image to identify one or more features relevant to the composition of the electronic image, each such feature having one or more compositionally significant properties from amongst a plurality of different predetermined compositional properties, and each such feature occupying a sub-region of the electronic image. Then the device selects one or more compositional rules from a set of predetermined compositional rules, based on the relevance of the compositional rules to the compositionally significant properties of one or more of the identified features. Then the device determines one or more suitable crop boundaries by applying one or more of the selected compositional rules.